“Collapse” is quite a bold title for a play that proves so trite. Built on unbelievable situations and uninspired jokes, the script holds enough humor to sustain a sitcom. But as this comedy stretches toward an hour and a half, the only thing that the title invites is an easy attempt to sum up the show.

As the story opens, we find the pants-less Hannah (Hannah Cabell) bent over in front of her husband, David (Elliot Villar), in what looks to be a sex act. Oh, ha ha, it’s not — after a string of sophomoric double-entendres we learn that David is giving Hannah fertility drugs. Within minutes they are interrupted by Susan (Nadia Bowers), Hannah’s wacky sister. She’s arrived from halfway across the country, unannounced, with plans to move into the couple’s home, uninvited.

Susan reveals that she’s involved in a drug-smuggling operation, but not before Hannah is talked into attending a support group in place of David, who is plagued by emotional problems. Along the way Hannah gets lost and meets Ted (Maurice McRae), a member of Sex Addicts Anonymous, and they go out for coffee. Sometime later these four characters all end up in a park to tangle with an apparent drug runner, David’s anxiety and a far-fetched case of mistaken identity.

From David’s penchant for emptying his beers into a living-room houseplant (for a cheap visual gag — what, is something wrong with the sink?) to Hannah’s compulsion to spill secrets to a stranger (for the convenient delivery of exposition) there’s not a shred of plausibility anywhere onstage. And yet that’s not insurmountable — good comedy often requires a generous suspension of disbelief, as does farce.

But the humor here never rises above the level of a “Three’s Company” episode (Susan: “You’re the one who seems edgy.” Hannah, yelling: “I’m not edgy!”) while none of the scenes are sharp enough for satire. And the introduction of serious topics that we’re asked to approach realistically and sincerely (like post-traumatic stress disorder — David was injured in the Minneapolis bridge collapse of 2007 and remains anguished) can even feel exploitive.

The actors, to their credit, rarely seem fatigued despite the manic mood, with Ms. Bowers and Mr. McRae working particularly hard to bring some nuance to their characters. Lee Savage’s spare set design does a lot with the limited space on Stage II at City Center.

Though “Collapse,” written by Allison Moore and directed by Jackson Gay, nods toward an idea or two about the economic slowdown, the tension usually feels artificial. This is a play that asks for a large amount of indulgence, then offers only a little imagination in return.